Isolation And Screening Of Rhizosphere Growth-promoting Bacteria In Pepper And Disease Resistance

China is the largest country of pepper producing.Continuous cropping is a common problem with the area of pepper cultivation growing expand.Continuous cropping exacerbates soil-borne diseases and seriously affects pepper production.In this study,PGPR were isolated from pepper rhizosphere soil and identified by molecular biological identification methods.The strains which have the ability of nitrogen fixation,phosphorus release and IAA secretion were investigated and explored the effect of promoting-growth by pot experiment.Screening strains with the ability of disease resistance of four pepper pathogens and explored the effect of strains on four capsicum diseases by pot experiment.The strains subjected to single factor experiments and orthogonal test were used to determine the potimal culture conditions.The main results were as follows:1.Fifty-eight strains were isolated from pepper rhizosphere soil.Among them,13 strains were identified by molecular biology and morphological characteristics,which belong to Bacillus,Pseudomonas,Lelliottia,Siccibacter,Achromobacter,Microbacterium and Paenibacillus;2.Screening of growth-promoting strains.13 PGPR were screened all had the ability to nitrogen fixation,7 strains could dissolve organic phosphorus,5 strains could dissolve inorganic phosphorus,and 3 strains had the ability to secrete IAA.3.N1 was the best strain for promoting the growth of pepper seedlings by the pot text.After20 days treatment of pepper seedlings,the plant height,root length,stem thickness,fresh weight,dry weight and relative chlorophyll content of pepper seedlings increased by 21.90%,10.98%,21.00%,60.56%,44.50%,17.11%.The effect of promoting growth is significant.4.N1,N7,N12,N16,and T22 have the ability to inhibit the growth of pathogenic fungi.T22 and N12 have disease resistance to 4 pathogenic bacteria of pepper(Rhizoctonia solani,Phytophthora capsici Leonian,Colletotrichum capsici bulterg and Fusarium oxysporum).The disease resistance of N7 and N16 to Rhizoctonia solani was better,and the inhibition rates were74.98 % and 75.87%.5.Pot experiments showed that PGPR had a certain control effect on pepper disease.After treatment with PGPR,the disease index of the plants decreased significantly.The control rate of N12 to Anthracnose was 40.63%,to Fusarium wilt was 46.34%,to Phytophthora blight was29.27%..Under pathogenic fungal stress,the activities of the defense enzymes(SOD,POD,and CAT)after the treatment of PGPR were significantly increased compared with the control group.6.Optimization of strain culture conditions.The optimal fermentation conditions of strain N1 were beef extract concentration 2%,soluble starch 2%,pH 7,peptone concentration 2%,soluble starch 2% and pH 7.